S B 



ITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 829 

Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



October 29, 1919 



THE 

MOSAIC DISEASE OF SUGAR CANE 

AND OTHER GRASPS 

E. W. BRANDES 

I) 

Pathologist, Office of Sugar-Plant Investigations 



CONTENTS 



History of the Disease 1 

Distribution in the United States ... 4 

Losses in the United States ... 7 

Primary Symptoms 8 

Secondary Symptoms 10 

Injuries Resembling Mosaic 12 

Varietal Susceptibility 12 

Varieties Attacked 12 

Immune Varieties 14 

Other Hosts 15 

Nature of the Disease 16 

Infection Phenomena 16 

Transmission of Mosaic in Diseased 

Seed Pieces 18 



Nature of the Disease — Continued. Page 
Transmission of the Disease by Car- 
riers 18 

Soil Relations 19 

Relation to Disinfectants 20 

Relation to Fertilizers 20 

Control 20 

Elimination by Roguing 21 

Elimination by Grinding All Cane 

and Securing-CIean Seed .... 22 

Exclusion 22 

Eradication .... * 23 

Elimination by Planting Immune 

Varieties 24 




WASHINGTON 
GOVERNMENT PRINTING OFFICE 

1919 





Book .M75 j g7 



-^M^' 



/ 3 



UNITED STATES DEPARTMENT OF AGRICULTURE 




BULLETIN No. 829 « 



Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 




jrL«^'V«-rt» 



Washington, D. C. 



PROFESSIONAL PAPER 



October 29, 1919 



THE MOSAIC DISEASE OF SUGAR CANE 
AND OTHER GRASSES. 

By E. W. Brandes, 

Pathologist, Sugar-Plant Investigations; formerly Pathologist, Porto Rico Agricultural 
Experiment Station, Mayaguez, P. R. 



CONTENTS. 



Page. 

History of the disease 1 

Distribution in the United States 4 

Losses in the United States , 7 

Primary symptoms 8 

Secondary sjTuproms 10 

Injuries resembling mosaic 12 

Varietal susceptibility 12 

Varieties attacked 12 

Immune varieties ^ 14 

Other hosts 15 

Nature of the disease 16 

Infection phenomena 16 

Transmission of mosaic in diseased seed 

pieces 18 



Page. 

Nature of the disease — Continued. 

Transmission of the ■disease by carriers . 18 

Soil relations 19 

Relation to disinfectants 20 

Relation to fertilizers 20 

Control 20 

Elimination by rogumg 21 

Elimination by grinding al! cane and secur- 
ing clean seed 22 

Exclusion 22 

Eradication 23 

E limination by planting immune varieties . 24 



HISTORY OF THE DISEASE. 

The mosaic disease of sugar cane, the presence of which has 
recently been discovered in Louisiana and other Southern States, 
is the malady that in epidemic form has occasioned severe losses m 
parts of Porto Rico during the past four years. There it has been 
variously called matizado, "mottlings;" rayas amarillas, "yellow 
stripe;" morida de perro, *'dog bite;" la enfermadad de Arecibo, 
"disease of Arecibo;" la enfermadad nueva, "new disease;" etc. 
The disease was first noticed in Porto Rico about the middle of 
1916. 

Starting from some point near Arecibo, on the north coast of 
Porto Rico, it spread rapidly over the cane fields to the west, down 
the west coast to the south coast, and up into the valleys and hilb 



4 BULLETIN 829, V. S. DEPARTMENT OF AGRICULTURE. 

of transmission was not present or at least not abundant in this 
region, it lias spread very little. At Santiago de las Vegas it was 
found on plants recently imported from Louisiana and from Tucuman, 
Argentina. The latter plants had come originally from Java. The 
disease had spread from these plants to an adjoining field of the native 
Crystalina cane. In view of this demonstration of its ability to 
spread at Santiago, it is very fortunate that the diseased plants were 
early observed and destroyed. A slight infection has been found at 
Mercedes, also as the result of a recent importation. 

Infected cuttings have been received in both Porto Rico and Cuba 
from Tucuman, Argentina, but to what extent the disease is prevalent 
in Argentina has not been learned. • 

Last year the mosaic disease was found in abundance at La Romana 
and the city of Santo Domingo, Santo Domingo, and less plentifully 
at Samana, La Vega, Monte Cristi, and Bonao.^ Lastly it was dis- 
covered at St. Croix, Virgin Islands, on cane imported from Porto 

Rico.i 

DISTRIBUTION IN THE UNITED STATES.^ 

The presence of the mosaic disease in the United States was first 
suspected when an agent of the Office of Sugar-Plant Investigations 
of the LTnited States Department of Agriculture discovered young 
diseased cane in Porto Rico from seed cane imported from Louisiana. 
The plants were so young at the time that secondary infection seemed 
improbable, and it was assumed that the seed pieces were diseased 
when shipped from Louisiana. Accordingly another agent of the 
same office visited Louisiana and on July 7, 1919, confirmed the 
presence of mosaic there. The State authorities were apprised of this 
important disclosure, and the Government agent made a hurried 
reconnoissance of the Gulf States, which reveajed the fact that the 
disease was already quite widely distributed there. 

On account of the infectious nature of the malady and the fact that 
it has caused severe losses in other cane countries, a complete sur- 
vey of the Southern States was immediately instituted to determine 
the location of all infested areas and, if possible, to trace the original 
importation of the disease and the course of its subsequent spread. 
Infested areas have been well delimited. The disease has been found 
by inspectors of the United States Department of Agriculture in 
Louisiana, Florida, Georgia, Alabama, and Mississippi (fig. 1). It 
is most abundant in Louisiana, as would be expected. There the 
river district is already badly infested. As far north as Angola, in 
West Feliciana Parish, several fields in a large plantation were found 

1 Stevenson, John A. The mottling disease of sugar cane. In Jour. Dept. Agr. and Labor, Porto Rico 
in press). 

2 Thanks are due to Mr. W. G. Taggart, vice director of the University of Louisiana Sugar Cane Experi- 
ment Station, and to Dr. C. W. Edgerton, pathologist, Louisiana Experiment Station, for courtesies 
extended to the writer and suggestions facilitating the survey in Louisiana. 



MOSAIC OF SUGAE CANE AND OTHER GRASSES. 5 

in wliich 75 per cent or more of the plants had the mosaic disease. 
From tliis point south to Donaldsonville, however, the amount of 
infection is not heavy. Many pLmtations are entirely free from 
mosaic, so far as can be determined by inspection. From Donaldson- 
ville to New Orleans an increasing amount of infection was recorded 
by the inspectors. Between Lutcher and Keserve, about 75 per cent 
of the plants in every plantation were infected. This is by far the 
m.ost heavily infested large area in the United States. From this 
region to New Orleans and from New Orleans to the lower extremity 
of the river district the amount of infection ranges from 4 to 30 per 
cent. Just a few fields were visited where no mosaic was found. 




Fig. 1.— Map showing the location of diseased areas of sugar cane in the United States. 

In the Bayou Lafourche district mosaic was found in only about one 
out of four fields visited and where present amounted to only 1 to 8 per 
cent of the plants. In the Bayou Teche district no mosaic was 
found on plantation cane, although nearly 500 fields were carefully 
inspected. A few cases were found in this region on cane recently 
distributed by the State Sugar Experiment Station. The imme- 
diate destruction of these few sources of infection is a matter of great 
importance. No mosaic whatever was found west of Bayou Teche 
or in Avoyelles and Rapides Parishes to the north. Thus, a very 
considerable part of the sugar-cane lands of Louisiana is stiU free 
from the disease, and every efi'ort should be made to keep it free. 

In Georgia the worst infested region is in the vicinity of Cairo, 
Grady County. There the proportion of infection ranges from less 
than 1 to 75 per cent or more in fields where the disease is present. 



6 BULLETIN 829, U. S. DEPAETMEIsTT OF AGRICULTURE. 

but only about one-fourth of the cane fields in this county harbor 
the infection at all. The affected area is quite sharply delimited, all of 
the disease being confined at present to farms located on the high- 
ways leading out from Cairo. The cane fields in Georgia consist 
usually of a few acres grown for sirup making. It is quite possible 
that by prompt and energetic action this community could free 
itself from the mosaic disease in short order. 

Cane fields are distributed over practically the whole State of 
Florida, but the crop is grown largely for sirup for home use and 
the cane patches are even smaller than those in Georgia. Mosaic 
has been widely scattered over the State by the distribution of cut- 
tings from experimental plats grown for the purpose of testing 
varieties. There are only two points, however, where the disease 
has spread so as to include any considerable area, namely, the vicini- 
ties of Marianna and Bristol. Other points in Florida where mosaic 
has been found include Apalachicola, Tallahassee, Punta Gorda, 
Palmetto, De Land, Winterhaven, Chattahoochee, Muscogee, and 
Canal Point. These are all purely local, infections, and in some cases 
the disease has not j^et spread more than a few rods from the 
original plantings shipped in from other States. An eradication 
. campaign would be entirely practicable in Florida. 

Mosaic has been discovered at only one point, Biloxi, in Mississippi. 
From the farm on which it first appeared it spread to one other farm 
in the vicinity. 

In Alabama similarly, it was found only on one place, near Mus- 
cogee, Fla. It was confined to the farm where it first appeared. 

Final reports on the results of the inspection in Texas must be 
deferred, since the survey is still under way in that State. 

The survey has also been very illuminating concerning the prob- 
able time of introduction of the disease into this country and the 
method of its subsequent spread here. Since 1913 a prohibitory 
regulation has been placed upon the introduction of sugar cane into 
the continental United States, and it is probable that no cane has 
been introduced since that time. Prior to 1913 varieties of sugar 
cane were imported naany times by private individuals and by various 
Government agencies. The Sugar Experiment Station of the Louisi- 
ana State University, at Audubon Park, has been particularly active 
in importing new varieties, with the idea of securing some higher in 
sugar content and yield than those already grown here. Wliether the 
mosaic was introduced by the experiment station or by private indi- 
viduals no particular blame attaches to those who are responsible for 
the importation of thi& obscure disease. There is no known method 
by which the presence of the disease in cuttings can be positiv/ely 
established. It is merely pointed out that such an importation 
would be practically impossible with the present quarantine against 



»i 



MOSAIC OF SUGAi; CANE AND OTHER GRASSES. 7 

sugar cane. Concerning the probable time of the importation that 
was responsible for the present wide distribution of mosaic in Amer- 
ica, the survey has brought out the fact that the distribution of cut- 
tings by the Louisiana Sugar Experiment Station in 1914 and prior 
to that time has not resulted in establishing the disease at the points 
where such cane was received. Since 1914, however, every point 
receiving seed from the station has become the center of a larger or 
smaller infected area. The inference, of course, is that while the 
disease may have been present at the station for a few years prior 
to 1914, it had not become so widespread that every seed shipment 
from there contained some infected cuttings. At the present time, 
about 97 per cent of the cane plants at the station have the mosaic 
disease. It is probable that private individuals have imported cane 
with this disease, but such cane is not likely to be widely distributed, 
and its spread, therefore, must depend upon natural agencies, a 
much slower process. 

Without exception, every infested area in Georgia and Florida can 
be directly traced to distributions of seed, cane from the Sirup Field 
Station at Cairo, Ga., since 1916, and the infection at this station 
dates from the importation of a number of varieties from Audubon 
Park in 1915. In nearly every instance where diseased cuttings 
have been received from Cairo, it has resulted in secondary infection 
of the surrounding native cane. 

The above is the brief and much condensed compendium of a large 
amount of data collected during July, August, and September, 
1919. It has made possible the recommendation of plans of attack 
upon the mosaic disease, which vary slightly in the different cane 
regions of the country, but all of which, if strictly adhered to by every 
cane planter, will bring the disease under control. Its capacity for 
rapid spread, as demonstrated in Georgia and Florida, means that 
a lapse of one year will result in immeasurably complicating the 
problem of ultimate eradication. 

LOSSES IN THE UNITED STATES. 

Since the mosaic disease had been unrecognized m this country until 
the writer announced its presence m July of this year, no extensive 
data have been accumulated to determine whether the losses caused 
by it in the United States are comparable with those sustained m Porto 
Kico. A few figures (Table II) have been obtained in Louisiana, 
however, which indicate that we may expect a decrease in yield 
almost equal to that in Porto Rico if the disease is permitted to 
become as widespread here as it is in that country. Losses here are 
held in check somewhat on account of frequent replanting. It has 
been noticed that where mfected sugar cane is allowed to ratoon over 
a long period of years that losses due to the mosaic are more severe 



8 BULLETIN 829, U. S. DEPARTMENT OF AGRICULTURE. 

each successive year. The figures m. Table II were ob tamed by 
cuttuig all of the cane in approxunately square patches of about 
one-tenth to one-fifth of an acre selected in commercial fields and 
in the fields at the Sugar Experiment Station, Audubon Park, La. 
The stalks cut from such patches were then sorted into two classes, 
diseased and healthy, and the average weight of stalks in each class 
was determined. The patches were not selected at random, but an 
attempt was made to find areas where the mosaic was doing a maxi- 
mum amount of damage and at the same time a sufficient number of 
healthy plants were present in the patches, growing under identical 
conditions, in order to make a fair comparison possible. Since, if 
no attempt is made to control the disease in these fields, we may 
expect ultimately to find an infection of 100 per cent, the losses wiU 
then be equivalent to the figures found in column 5 of Table II. 

Table II. — Tests of sugar cane in Louisiana, showing the extent of losses in different 

varieties. 



Variety. 





Average weight of 


Reduc- 








stalks — 


tion in 
weight of 
diseased 


Diseased 

stalks in 

field. 










Healthy. 


Diseased. 


Healthy. 


Diseased. 


stalks. 








Pounds. 


Pounds. 


Per cent. 


Per cent. 


330 


160 


1.13 


0.7 


38 


32 


268 


100 


1.507 


1.22 


19 


27 


204 


lOS 


1.27 


1.03 


18 


34 


348 


136 


1.65 


1.16 


29 


28 


373 


310 


.874 


.787 


10 


45 



Loss in 
tonnage. 



Louisiana Purple. 
Louisiana Striped 

D-74 

D-95 

L-511 



Per cent. 
12.16 
5.13 
6.12 
8.12 
4.5 



PRIMARY SYMPTOMS. 

Upon walking between the rows of cane in an affected field, more 
or less plants will be seen that are conspicuous on account of a gen- 
eral pallor of the leaves. This may be discernible for many rods. 
Closer examination of such plants reveals that the pallor is due to 
irregular light-colored streaks or spots on the leaves. The affected 
leaf areas, in so far as color is concerned, are of two distinct types. 
The most common type presents merely a ''washed-out" appearance. 
It is, in fact, merely a tint of the normal color, in which the blue and 
yellow are present in the same proportions but diluted. In the sec- 
ond type, the yellow is predominant, and the affected areas have a 
decided yellowish green appearance. The normal and affected areas 
are sharply demarked. In other words, there is no gradual merging 
of one color into the other. There is a great diversity of patterns 
in the different varieties, due to the variation in the amount, size, and 
shape of the light-colored areas, but the arrangement is so constant 
in any particular kind of cane that the character could be used as an 
aid in determining varieties. 



MOSAIC OF SUGAR CAI^TE A:firD OTHER GRASSES. 9 

Among the cane varieties commonly grown in Louisiana and other 
Southern States, some rather constant differences occur in the expres- 
sion of the mosaic disease. In L 511 it will be noticed that streaks 
are rather scant in newly invaded leaves and on account of their light 
color make a great contrast with the normal areas. They are bluntly 
pointed and range from one-sixteenth to three-sixteenths of an inch 
wide and from one-fourth of an inch to 3 or 4 inches long (PL I, fig. 4) . 
Later, the light areas or streaks are more numerous and in most 
cases tend to become confluent in well-defined bands of light tissue 
extending across the leaf at right angles to the midrib and alternating 
with bands where the light streaks remain isolated. These bands are 
from H to 2 inches long. The above condition is typical of the 
disease as it appears in L 511, but does not invariably occur. 

In D 74 the streaks are not usually isolated, even at first, so that 
very quickly the coalesced light areas are predominant and the nor- 
mal areas appear as irregular, elongated islands 1 thirty-second to 
three-eighths of an inch wide and of varying length, from one-fourth 
of an inch to several inches, as shown in Plate I, fig. 5. Affected 
areas are light green at first, but the tendency for the whole leaf 
to become opaque yellow is pronounced. 

In purple cane the light areas are elongate and isolated at first, but 
later they predominate and coalesce and the normal green shows as 
irregular elongated islands, as illustrated in Plate I, fig. 5. The islands 
are not of uniform width or length. 

In the youngest leaves of Ribbon cane, the light areas are in the 
shape of attenuated streaks, usually about one-eighth of an inch wide 
and one-half of an inch to 1^ inches long, but the size varies greatly, 
some streaks being very minute, and others, by running together at 
the ends, form continuous stripes 6 inches or more in length. In 
general, the streaks are isolated from one another and uniformly dis- 
tributed on the leaf blade as in Plate I, fig. 4. The amount of nor- 
mal-colored tissue greatly exceeds the light tissue at this time. Excep- 
tionally, the light streaks may be confluent from the first, and this is 
more frequently seen near the midrib, leaving the margin normal in color 
orwith a fewscattered palestreaks. In slightly older leaves, by growth 
and confluence of the light-colored areas the latter becomes predomi- 
nant and the whole leaf becomes pallid or even yellow in its general ap- 
pearance. The dark-green or normal areas are now very scant, and 
they appear as elongated streaks in the pale green, just the reverse of 
the condition in young leaves, except that the dark-green streaks 
are less regular in outline. The individual streaks vary considerably 
in width and direction throughout their extent, streaks perhaps 
three-eighths of an inch wide at one end becoming constricted to 
1 thirty-second of an inch, then alternately widening and narrow- 
ing or becoming oT)lique with the midrib, with no apparent forces 
142481°— 19— Bull. 829 2 



10 BULLETIl!^ 829, V. S. DEPAETMENT OF AGRICULTURE. 

limiting their extent or direction except that in general they are 
elongated in the direction of the parallel veins of the leaf. 

In D 95 the light areas are predominant from the start (PI. I, fig. 5). 

In L 219 the light streaks are isolated near the base of the leaf but 
become confluent toward the tip. 

In L 226 the streaks are isolated and even in older leaves remain so. 

L 231 is very severely injured. The leaves are usually quite yellow, 
as shown in Plate I, fig. 6. Practically the entire surface is light 
from the beginning. There are exceptions, however. The amount of 
injury in this variety is variable. 

L 253 is quite tolerant. The lighter areas predominate but are not 
yellowish. All plants seen were dark green and vigorous. 

SECONDARY SYMPTOMS. 

Field observations covering a number of years indicate that the 
deleterious effects of the mosaic disease are cumulative. The streak- 
ing and spotting of the leaves discussed above are the only noticeable 
sign in newly infected plants. The disease is never fatal during the 
first year and, in fact, it rarely terminates in death even in diseased 
plants that have been allowed to ratoon for years. Usually, however, 
more serious effects are seen in first ratoons of cane which became in- 
fected the previous year or in plant cane originating from diseased 
cuttings. At this time another quite distinct leaf symptom appears. 
It consists of small white opaque spots and streaks in the light-colored 
areas. These streaks are sm.aller than the light areas previously men- 
tioned and differ from them in having no pigment whatever. They 
range from mere points to elongated irregular streaks several inches 
in length. The white streaks may become confluent to a limited 
extent. They are for the most part restricted to the light-green areas 
of affected leaves, but do not correspond to them in outline and 
typically remain more or less isolated from one another. The white 
opaque tissue has a dried-out appearance and seems to be quite 
functionless. It remains firm, however, and does not become brown 
or rot out. The amount of total leaf area occupied by this type 
of tissue rarely exceeds 20 to 30 per cent of the whole. 

At about the same time, or during the next year, a still more in- 
jurious sign of mosaic appears, namely, the striping or cankering of 
the stalk. This is much more marked in some varieties than in 
others. Ordinarily, it does not become noticeable until the cane is 
quite w^eU developed. By tearing away the enveloping leaf bases, 
cankers can sometimes be found in the mcipient stage. They appear 
as discolored or water-soaked patches or longitudinal streaks on the 
internodes. In severe cases these areas become siuiken and the 
internodes are spindle shaped and attenuated. Longitudinal cracks 
may appear, resulting in the drying out of the cane. There is a 
tendency toward shortening of the joints and premature development 



U. S. DEPARTMENT OF AGRICULTURE 
BUREAU OF PLANT INDUSTRY 



THE MOSAIC DISEASE OF SUC 




1.— A short piece of healthy leaf of the Immune varietyKavan- 
gire. 




2.— A piece of leaf of variety B-3922, showing isolated, more 
or less rounded and irregular patches of normal color on a 
background of pallid, affected tissue. 




3.— A piece of leaf of variety D-1 17, showing a mosaic pattern 
somewhat similar to the above, but finer. 



PLATE 



CANE AND OTHER GRASSES. 




<+.— « rnrrwT'L'i ivp" '■ r-':v,,ne, irrK:Jji;u streaks Of pallid 

green, of unequal length and width but elongated in the direc- 
tion of the long axis of the leaf, on a background of normal 
green; on leaf of variety Rayada. 




5. — A pattern somewhat similar to the above, but with the 
colors reversed, so that the pallid green predominates; on leaf 
of variety G. C. 1479. 




6.— The most injurious of the common types of mosaic. Just 
a few streaks or islands of normal green remain on a back- 
ground of yellowish green ; on leaf of variety M. P. R. 2. 



^ 



1 



MOSAIC OF SUGAR CANE AND OTHER GRASSES. 



11 



of roots and shoots at the nodes of standmg cane. Figure 2 shows 
such a condition in Yellow Caledonia cane. The photograph repro- 
duced here was taken at Arecibo, Porto Rico, in 1919, and the 
probabilities are that the plant had been infected for at least five 
years. These iden- 
tical cuttings and 
similar ones were 
brought to Washing- 
ton and planted in 
a quarantine green- 
house. Most of them 
grew, but at the pres- 
ent time, five months 
after planting, they 
are scarcely 1 foot 
tali. The opaque 
white streaking 
covers practically all 
of the leaf area. This 
is the most excessive 
injury ever observed 
by the writer. Most 
varieties of cane do 
not go to pieces like 
this, but rather the 
injury to stalks con- 
sists merely of re- 
tarded development. 
Among the well- 
known varieties, 
however, all grada- 
tions in the extent of 
injury between these 
two extremes are to 
be found. 

When a large pro- 
portion of the plants 
in a field are infested, 
the aspect in general 
resembles the effect 
of a severe drought. 
The foliage of the entire field is yellowish, and the plants are more or less 
noticeably stunted. Where a row of some immune variety is planted 
in or near a badly infested field, the contrast in color is exceedingly 
conspicuous and the dwarfed habit of infected plants is more notice- 




FiG. 2. — Canker stage in Yellow Caledonia sugar cane; healthy cane of 
the same variety in center. 



12 BULLETIN 829, U. S. DEPARTMENT OF AGRICULTURE. 

able. It is possible to recognize such fields from a distance of half a 
mile or more on account of their sickly, dry appearance. 

INJURIES RESEMBLING MOSAIC. 

Many types of injury are commonly fomid on cane leaves that 
might be confused with this malady by one not familiar with it. 
The condition termed chlorosis, which is due for the most part to 
soil conditions, expresses itself in many ways, some of which closely 
simulate the mosaic disease. The affected areas are white opaque 
or yellow, and the most familiar form is a regular striping of the leaves 
longitudinally. The stripes usually extend the entire length of the 
leaves and may be about one-eighth of an inch wide and numerous, 
with normal green stripes of equal width spaced between them, or 
the chlorotic areas may be quite wide. Occasionally, the entire leaf 
is pure white. Less frequently the areas are in the form of large 
spots or blotches, extending inward from the margins of leaves or 
situated at the center of the blades anywhere from base to tip. 
Another type, which is rare, consists of a very fine irregular white 
mottling of the leaves, which, however, is in local patches and does 
not involve the whole leaf, as is invariably the case with the mosaic 
disease. Many fungi cause spotting of the leaves of cane, but these 
can easily be distinguished, as the spots usually turn broAvn and the 
leaf tissue dies, which does not occur in the cane mosaic. Since a 
pale-green halo is sometimes present surrounding these small spots, 
they have the appearance of mosaic from a distance, especially 
when quite numerous, but a close examination always reveals quite 
distinct differences. Many insects, especially those which feed by 
pimcturing the leaf epidermis and sucking the sap from the layere 
of cells below, cause a very fuie mottling of the leaves when the 
punctures are present in enormous numbers. Ordmarily, the punc- 
tures are scattered and can lead to no confusion. This type of in- 
juiy can also be determined by close inspection, since the minute 
pale area surrounding each individual puncture is almost exactly 
circular and has no tendency to elongation in the direction of the 
long axis of the leaf, such as is almost invariably the case in true 
mosaic. Drought, lack of proper nutrients in the soil, excessive 
rainfall, and poor tilth, or combinations of these, sometimes result in 
a general pallor or yellowing of the leaves, but this color is always 
uniform and can lead to no confusion. 

VARIETAL SUSCEPTIBILITY. 

VARIETIES ATTACKED. 

More than a thousand varieties of cane have been determined to be 
susceptible to the mosaic disease. Most of these are the progeny of 
seedling canes that exist in small variety-test rows or patches at the 



MOSAIC OF SUGAR CANE AND OTHER GRASSES. 13 

various sugar-cane experiment stations, but the list includes also 
practically all of the commercially esteemed sorts grown for the mills 
on a plantation scale. 

3o far as can be learned, none of the varieties grown in Java is 
truly immune, but a high degree of resistance or tolerance of the 
disease has been observed in the favorite Java seedling canes grown 
in Porto Rico, a probable explanation of which has already been given. 
Only Java 56, 100, 228, and 234 have been seen by the WTiter in 
Porto Rico, but all of these, though 100 per cent of the individuals 
were affected, made a tlu-if ty growth and produced apparently normal 
stalks. The leaves arc not noticeably yellowed, but on the contrary 
appear to be of uniform dark-green color when viewed from a dis- 
tance. Close inspection, however, shows the characteristic streaks, 
but the diseased areas are very little lighter than the normal areas. 
Probably the damage done to an individual plant is slight, but the 
aggregate damage to all of the individuals in a field is a measurable 
quantity and has been shown to be quite considerable in Java. In 
the different varieties all degrees of tolerance are exhibited, ranging 
from the higlily resistant Java canes down to the soft white Otaheite 
or Bourbon cane, which is so severely injured that the cane is hardly 
worth milling. In addition to the conditions which might be termed 
varietal tolerance of the disease, some varieties exhibit decided and 
rather constant differences in the percentage of individuals that 
become affected under the same conditions. This is brought out in 
variety-row tests where the same varieties have been planted at 
several points in the same field. Under these conditions it has been 
found that some varieties will show a 100 per cent infection of the 
individuals in all of the rows, while in others perhaps only 60 per cent 
of the plants will be diseased in each of the separated rows or plats. 
It seems reasonable to suppose that all varieties were equally exposed 
to the contagion in such situations. This fact indicates a possibility 
of resistant strains among the individuals of a variety. 

The Rayada or Striped cane and- the Crystalina or Wliite Trans- 
parent, the two favorite varieties in Porto Rico, are severely injured. 
Yellow Caledonia is grown on a large scale in some localities, and 
plants of this variety killed by the mosaic disease have been observed. 
This is quite unusual, since attacked plants of most varieties become 
badly stunted but do not die. All seedling canes from Demerara 
and Barbados grown in Porto Rico are attacked. Seedlings of the 
Insular and Federal agricultural experiment stations likewise are aU 
affected, as are the seedlings originated at Centrals Guanica and Fa- 
jardo. Among the varieties planted commercially to a limited ex- 
tent the Bambu, Cavengerie, Morada, and, in fact, all the broad- 
leaved canes have proved to be susceptible. 



14 BULLETIN 829, U. S. DEPARTMENT Ol^ AGRICULTURE. 

Ill Cuba all varieties that are exposed seem to become infected, 
but since the disease has not become rampant nor spread over any 
considerable area no opportunity to observe the reaction of all the 
varieties grown there is to be had. Practically aU of the seedlings 
origmated in the Harvard Experiment Station near Cienfuegos were 
affected, as well as the imported Ja^^^a 228, L 511, and the native 
Crystalina at Santiago de las Vegas. 

Practically all varieties are attacked in the Hawaiian Islands, and 
extensive damage is done. 

The common varieties in Louisiana have proved susceptible to 
mosaic disease. Louisiana Purple, Louisiana Striped, D 74, D 95, 
L 511, L 218, L 219, L 226, L 231, L 253, and hundreds of seedhngs 
being tested at the Louisiana Sugar Experiment Station all fall prey 
to the ravages of this disease. 

IMMUNE VARIETIES. 

Fortunately a few varieties of sugar cane have been discovered 
which appear to be entirely immune. Most of them are of the 
slender North India type, generally known as Japanese canes. The 
Kavangu-e, a variety which, because of its prolific stooling, yields a 
very large tonnage and is much esteemed in Argentina for making 
sugar has never been observed to be diseased, although it has been 
exposed to infection for four years in the worst infested regions of 
Porto Rico.^ It is a rather long season cane, however, and for this 
reason is probably not suited to Louisiana conditions. Another Jap- 
anese cane, Cayana 10, which is becoming prominent in the sirup 
sections of Georgia and Florida, is also immune. This variety has 
already met with considerable favor on the part of cane growers in 
Georgia. All the other Japanese varieties observed, including many 
imported by the Office of Foreign Seed and Plant Introduction of 
the Bureau of Plant Industry, have been found to be uniformly free 
from this disease. 

Among the broad-leaved thicker stalked varieties several kinds 
have been found that appear to be immune, but our evidence of their 
immunity is not so complete as is the case with the Japanese varieties. 
Louisiana seedlings 1646, 1606, 1674, and 1797, growing in the 
variety test plats at Audubon Park, New Orleans, this year appeared 
to be immune. No individuals of these varieties were diseased, 
although they were surrounded by other varieties, the individuals 
of which averaged 97 per cent diseased. 

1 Townsend, C. O. An immune variety of cane. (Abstract of an article by F. S. Earle.) In Science, 
n. s., V. 49, no. 1272, p. 470-472. 1919. 



MOSAIC OF SUGAE CANE AND OTHER GRASSES. 15 

OTHER HOSTS. 

A number of other grass plants are known to be subject to the 
mosaic disease, but apparently they are attacked with difficulty 
and only under conditions favorable to the disease. Among these 
hosts are corn, sorghum, rice, millet, crab-grass, foxtail, and Panicum. 
Probably the list of susceptible plants is much larger, but up to the 
present time opportunity for testing others has not been had. In 
the case of corn, rice, and millet, we have no experimental proof that 
the diseases are the same, but must depend upon field observations. 
If not the same, the disease must be very similar, since the leaf 
symptoms are identical. The characteristic streaked and spotted 
appearance of the leaves is present in all attacked plants. 

With regard to sorghum, crab-grass, foxtail, and Panicum our 
evidence is conclusive and j^roves that the infectious material or virus 
is the same for all of these plants. Sorghum seed of the Early 
Amber, Sugar Drip, and Japanese Ribbon varieties was sown in a 
bed at the quarantine gi'eenhouse at Washington, where diseased 
plants of 17 different varieties of sugar cane were growing. When the 
sorghum plants were about half grown, practically all of them began 
to produce mottled leaves and continued to do so until they went to 
seed. 

The seed was saved from these sorghum plants to determine whether 
the disease is transmitted to the next generation in the true seed.^ 
The leaf symptoms in these greenhouse plants were exactly like the 
symptoms on sugar-cane leaves. Plants arising from the same batch 
of seed used in the greenhouse experiment cited above but planted 
elsewhere and not exposed to the disease did not show the phenomenon 
but produced healthy leaves of uniform color. The crab-grass, fox- 
tail, and Panicum came up as volunteer plants in the quarantine 
greenhouse. Scores of stools of these weeds were allowed to mature 
for observation and identification. Every plant became infected 
and exhibited the typical leaf symptoms. Some half dozen other 
species of wild grasses were present in the greenhouse, but they were 
not attacked. All of the wild grasses were abundant outside of the 
greenhouse, but in spite of an assiduous search in the vicinity not 
a single infected plant could be found. The conclusion to be drawn 
from these observations is obvious. We are not dealing with similar 
mosaic diseases of these various graminicolous hosts, the viruses of 
which are specific for each host, but with one and the same disease. 

The existence of other host plants, especially the common wild 
grasses, would appear to be one of the most alarming of the recent 
developments in the problem. It is needless to say that the control 

1 This seed was planted in flats. At the present time, three weeks after germination, no sign of the mosaic 
has appeared. 



16 BULLETIN 829, U. S. DEPARTMENT OF AGKICULTURE. 

of the disease would be immeasurably complicated if it were to be- 
come prevalent on such, omnipresent weeds. Fortunately, however, 
our observations appear to indicate that the grasses other than, cane 
become infected only under conditions favorable to the disease and 
in the near vicinity of infect'ed sugar-cane plants. Infected corn, 
for instance, has been seen by the writer only in Porto Eico, where 
it was growing between the rows of diseased cane stubble. Infected 
rice plants were observed there only once, growing just across a 
narrow dirt road from a badly attacked cane field. At Audubon 
Park, La., attacked sorghum was seen in a similar situation, the 
most remote plants being only about 3 rods from the cane, and the 
percentage of attacked plants decreased in an inverse ratio to the 
distance from the cane. The same was true of crab-grass, which 
was abundant in the sorghum field. These observations are en- 
couraging and tend to offset the disconcerting facts discussed above. 

NATURE OF THE DISEASE. 

INFECTION PHENOMENA. 

Sugar-cane mosaic is an infectious chlorosis, similar in many re- 
spects to the mosaic diseases of tobacco, cucumber, bean, tomato, 
and potato. Evidence of its infectious nature exists in hundreds of 
field observations and in the infection of experimental plants under 
controlled conditions. The well-defined epidemic in Porto Rico, in 
which it has been established that the disease started in a small local 
area and gradually spread from this focus of infection, diseased plants 
being confined within the limits of the ever-increasing infested terri- 
tory and not appearing sporadically at remote points, is convincing. 
It leads to the inevitable conclusion that some virus or inoculum is 
responsible for the appearance of new cases and that the only source 
of inoculum is some plant previously infected with the disease. No 
other explanation accounts satisfactorily for the observed facts. 
Climatic conditions were at first suggested, but the epidemic has 
lasted already for a period of years, during which rainfall, tempera- 
ture, sunshine, and the other factors that go to make up climate 
have been normal. The wearing out of soils was regarded as a 
possible cause, but during the steady progress of the disease it gradu- 
ally encroached upon every conceivable type of soil, including the 
richest and most productive in the island. Strong support was 
given to the idea that it was a case of deterioration or the "running 
out" of varieties, but when it became evident that all varieties 
present in the invaded district were affected, this idea was aban- 
doned. For the same reason the hypothesis that it is a case of bud 
variations, or "sports," seems highly improbable, and when the 
regular progress of the epidemic is borne in mind, radiating outward 



MOSAIC OF SUGAR CANE AND OTHER GRASSES. 17 

as it does from a common starting point, there is seen to be notliing 
to substantiate this claim. 

Only a few specific observations of infection may be cited in the 
limited space available. In October, 1918, healthy seed of about 80 
varieties was brought into the infested area from disease-free regions 
in order to determine whether any natural immunity existed among 
the varieties present in Porto Rico. This seed was planted at the 
Santa Rita estate, near Yauco. When the seed germinated, the 
young plants were seen to be healthy and normal, but within six 
weeks to two months practically every plant of all varieties with one 
exception (the Japanese Kavangire) showed the unmistakable symp- 
toms of mosaic. This was a clear case of secondary infection from 
the fields of diseased cane surrounding the test plat. 

At Santiago de las Vegas, Cuba, about 200 seed pieces of Java 228 
cane imported from Tucuman, Argentina, were planted in two rows, 
and two rows of the native Crystalina cane were planted beside them. 
The Java cane was 100 per cent infected when it came up, the cut- 
tings having come from diseased parent plants. When this planting 
was examined in June, 1919, 75 per cent of the Crystalina plants- 
were characteristically diseased. The Crystalina seed pieces had 
come from a field which was minutely searched and found to be en- 
tirely free from disease. No other cases were found in the entire 
region, in fact, with the exception of a single stool of L 511 imported 
from Louisiana. 

In July, 1919, a field of D 74 stubble cane, grown for sirup near 
Cairo, Ga., was found to be healthy with the exception of one corner 
near the kitchen garden, where about 80 per cent of the plants had 
the mosaic. Investigation revealed the fact that a patch of green 
chewing cane had been growing adjacent to the D 74 at that corner 
during the preceding year. The green cane was found growing else- 
where on the farm this year, and examination showed that every 
plant had the mosaic disease. Clearly the D 74 had become infected 
last year, the disease had survived the winter in the stubble, and the 
shoots were diseased when they appeared again. 

At Washington, D. C, 17 varieties of cane, all diseased, are growing 
in an insect-proof quarantine greenhouse.^ From time to time 
healthy sugar-cane plants in pots have been taken into the greenhouse 
and left exposed to the contagion. Invariably they show the incip- 
ient symptoms of the disease on the average in 17 days, proving that 
the incubation period is from two to three weeks. As has been men- 
tioned elsewhere, sorghum and wild grasses taken into this greenhouse 
have also become infected. Much more evidence of this kind could 
be adduced, but it is believed to be sufficiently clear that infection 

' Insects were present in the greenhouse. 



18 BULLETIN 829, U. S. DEPARTMENT OF AGEICULTURE, 

by some principle present only in dieased plants is responsible for the 
appearance of the disease in formerly healthy individuals. 

TRANSMISSION OF MOSAIC IN DISEASED SEED PIECES. 

Experiments in Porto Rico ^ and elsewhere have repeatedly demon- 
strated that cuttings from infected stalks invariably give rise to 
infected plants. The young shoots are seen to be mottled as soon as 
they appear. These are referred to as primary infections. The 
fact is one of far-reaching importance, and to it must be attributed the 
spread of the disease to new regions, remote from any infected cane, 
by shipments of cane seed. The use of diseased stalks for propagating 
results in wider distribution of diseased plants on the same planta- 
tion from year to year and insures the survival of the virus, even in 
the absence of secondary infections. Transmission of the disease in 
cuttings is a fact, the importance of which can not be overemphasized 
in view of its obvious bearing on control measures. 

TRANSMISSION OF THE DISEASE BY CARRIERS. 

It can be proved mathematically that by the law of chance the 
percentage of diseased plants in a plantation would tend to remain 
stationary from year to year provided there was no conscious or 
unconscious selection,^ if the spread of the disease depended wholly 
upon the use of infected cuttings. Nature has provided a far more 
efficient method for the quick dissemination of the malady. Second- 
ary infection, i. e., infection due to the inoculation of healthy plants 
during the growing season, goes on at a more or less rapid rate wher- 
ever the disease has been observed. Secondary infections are easily 
determined as such when the plants are young. In the case of plants 
infected in the greenhouse it has been determined that only the leaves 
which were immature at the time of inoculation and leaves subse- 
quently formed become mottled. When a plant is found with normal 
leaves up to a certain point on the stalk and mottled leaves above 
that point it is a clear case of secondary infection. Since in older 
plants the lower leaves are gradually sloughed off until only a 
relatively small terminal tuft of the youngest leaves remain when the 
plant approaches maturity, this method is obviously limited to 
young plants or to plants with green leaves still present above and 
below the point of inoculation. 

The rate of spread of the disease, as indicated by these secondary 
infections, varies greatly. Fields are frequently seen in which there 
has been apparently no secondary infection during an entire growing 

1 Stevenson, John A. The "mottling" disease of cane. Porto Rico Insular Exp. Sta. Ann. Rpt. 1916-17, 
p. 40-77. 1917. [Literature], p. 7&-77. 

2 Selection is employed where the disease is not recognized. During the beginning of the epidemic in 
Porto Rico, when sugar was bringing an unprecendented price, it was learned that the manager of one of the 
mills was instructed to grind the best cane and save the poorest for seed. The "poorest " was undoubtedly 
that attacked by mosiac. 



MOSAIC OF SUGAR CANE AND OTHER GRASSES. 19 

season. As an extreme case illustrating this point, the fields near 
Cienfuegos, Cuba, may be cited. There the disease has merely sur- 
vived by the planting of infected seed pieces, and secondary infection, 
if it goes on at all, is certainly very limited. Even in Porto Rico, 
during the height of the epidemic, secondary infection was at a 
standstill in some localities for a year or more. On the contrary, 
whole fields of healthy cane became infected in the short space of a 
month or two. Such a case was the invasion of the variety test field 
at Santa Rita, Porto Rico, previously mentioned. No doubt the 
explanation for this great variation in rate of spread by secondary 
infection must be sought in the . mechanics of inoculation. Up to 
the present no positive proof of the method by which inoculation is 
accomplished in nature has been brought forward. Reasoning from 
the fact that new cases often appear at some distance from diseased 
individuals, it would seem that some agent or carrier is* necessary. 
Mere contact of diseased and healthy plants does not serve to com- 
municate the infection from the former to the latter. In no case has 
the planting of healthy cuttings in the same pots with diseased plants , 
resulted in the new plants becoming diseased. The same holds true 
for plants in the field, where healthy plants are often seen with their 
leaves mingling freely with the leaves of diseased plants for a time 
much longer than the incubation period for mosaic, but with no 
evidence of transference of the inoculum. It is evident that special 
conditions are necessary in order that the disease can be communi- 
cated to healthy plants. 

Field observations indicate that acceleration in the spread of the 
mosaic disease is accompanied with or preceded by severe insect infesta- 
tions. The cane leafhopper (Tettigonia sp.) in particular has been 
noticed to accompany the rapid spreading of the disease. This evidence 
is incomplete, but it is supported by the fact that 10 healthy plants 
placed in insect-proof cages in the greenhouse at Garrett Park, Md., 
did not contract the disease, while five control plants outside of the 
cages, but otherwise under identical conditions, all became infected. 
Aphids were abundant on the diseased cane in this greenhouse, and 
a few leafhoppers were present. A great deal of experimental work 
remains to be done before formal proof of the responsibility of any 
particular insect or insects for the transmission of the disease can 
be offered, 

SOIL RELATIONS. 

There has been no indication that the contagion persists in the soil 
after a crop has been removed and the stubble plowed up. Fields 
that have been veritable hotbeds of infection after being plowed up 
and planted with clean seed have only a few scattered cases, which 
can be accounted for by faulty seed selection. Healthy cuttings 
planted in the soil of pots from which badly diseased specimens had 



20 BULLETIN 829, TJ. S. DEPAETMEISTT OF AGRICULTUEE. 

just been removed grew witliout any evidence of the disease. The 
virus does not live over in the soil and it is doubtful whether it exists 
there at any time. In this respect the mosaic does not by any means 
present the practical difficulties in the way of control measures to be 
met with in root-rot. Root-rot, in fact, is to be regarded as a far 
more serious problem for the Louisiana cane planter than mosaic on 
this account. 

RELATION TO DISINFECTANTS. 

Treatment of infected seed pieces by soaking in strong Bordeaux 
mixture or corrosive sublimate previous to planting has had no effect 
on the course of the disease. All shoots were typically mottled as 
soon as they appeared. It was hardly to be expected that superficial 
disinfection could influence the virility of the infectious principle when 
all our evidence indicates that the latter permeates the internal 
tissues, or at least the vascular systems of affected plants. 

RELATION TO FERTILIZERS. 

Many experiments ^ have been performed in Porto Rico to deter- 
mine the effect of applying fertilizers, since the claim was made by 
many planters that mosaic was due to insufficiency of plant nutrients 
in the soil. Filter press cake, sulphate of ammonia, and lime in 
various combinations, together with turning under cover crops and 
good tilth, had no noticeable effect on the disease as compared with 
control plats. Standard complete fertilizers were also tried. Beyond 
a slight stimulation in growth and the darker green color of the treated 
plants, there was no observed effect. Diseased plants may be expected 
to respond to good growing conditions the same as healthy ones, 
but the same constant difference between healthy and diseased plants 
is maintained under all conditions. The diseased stalks remain below 
the average weight for healthy stalks and are just as capable of 
spreading the disease. Liming the soil has no more effect on diseased 
plants than the application of fertilizers. 

CONTROL. 

It is interesting to note that in Java long experience has demon- 
strated that the disease can best be held in check by careful selection 
of healthy plants for seed and by replanting fields with cuttings taken 
from the same field, in preference to buying cuttings of imknown 
origin or moving the cuttings from field to field on the same plan- 
tation. The use of such methods practically amounts to tacit 
admission of the infectious nature of cane mosaic, although it is 
ascribed to "bud variation." The facts wliich have most impressed 
the Dutch planters are that cuttings from diseased stalks always 

1 Stevenson, John A. The "mottling" disease of cane. Porto Rico Insular Exp. Sta. Ann. Rpt., 
1916-17, p. 40-77, 1917. [Literature] p. 76-77. 



MOSAIC OF SUGAR CANE AND OTHER GRASSES. 21 

produce diseased plants and that careless importation of seed is 
apt to result in increased amounts of the disease. 

In the Hawaiian Islands also the disease is controlled by selection 
of clean seed and the use of resistant varieties. 

Measures for controlling the mosaic disease recommended in the 
following pages are not haphazard expedients, but have been used 
with very satisfactory results in Porto Rico for more than a year. 
Planters there have paid a heavy price to learn them, and it is urged 
that planters of sugar cane in the United States cooperate to prevent 
a possible epidemic. Indifference to the situation may result in the 
cane growers being confronted with the fact that it is too late to prac- 
tice seed selection, as is already the case in western Porto Rico. 
At present, it will work no particular hardship on the planters to 
take steps that will reduce the disease to a minimum. 

ELIMINATION BY ROGUING. 

Roguing consists of pulling out infected plants, root, stem, and 
branch, and throwing them down between the rows. It is based on 
the fact that as soon as the plants are wilted they are no longer 
dangerous as a source of infection. This method is applicable only 
to fields in which the disease has not obtained a strong foothold. 
It is not recommended for fields in which the number of infected plants 
exceeds 5 per cent in half -grown to mature cane or 20 per cent in young 
plants just sprouting. The size of the field and the condition of 
surrounding fields with reference to the occurrence of the disease 
in them must also be taken into consideration. When the field is 
quite small or consists merely of a few rows or plants of a new variety 
being propagated for trial on a plantation scale, it should be rogued 
even if 100 per cent of the plants are infected. Such plants are a 
constant menace to plants in surrounding fields. In large fields 
where the proportion of diseased individuals is greater than 20 per 
cent, roguing is impracticable, not because the plants are any less 
potent as sources of infection, but because diseased plants produce 
millable cane, and to destroy considerable quantities of such plants 
would probably result in greater financial loss than would be sustained 
by the reduction in yield due to new cases. Large fields with a high 
percentage of diseased plants should be allowed to mature, but no 
cane from such fields should be saved for seed. 

It is suggested that the foUowuig schedule of inspections and 
roguing be put into operation : In the spriiig, just as soon as all of the 
plants have sprouted, the fields should be inspected by passmg up 
and down the rows. All diseased stools should be puUed out of the 
ground and cast down between the rows. If this fu'st inspection is 
carried out in a thorough manner the field will be completely freed 
from the disease provided no secondary uifections are going on. 



22 BULLETIN 829, U. S. DEPARTMENT OF AGRICULTURE. 

Since there are as yet no certain means of determining the latter 
fact, a second mspection is essential. It should be made from 25 
to 30 days after the first, a lapse of time sufficiently in excess of the 
incubation period for mosaic to insure recognition of the disease in 
plants inoculated prior to the first inspection. If no diseased plants 
are found during the second inspection, it can be assumed that 
secondary infection is not in operation and that the remaining 
plants will continue healthy. If diseased plants are found, how- 
ever, it establishes the fact that secondary infections are going on. 
The field should be rogued as before, and a third inspection made 
after the same interval, i. e., 25 to 30 days. If the carriers remain 
active it may be necessary to repeat the process several times, and 
owuig to the impossibility of recognizing the disease in inoculated 
plants before the end of the incubation period it is certain that 
plants which have become infected just before the inspection is 
made will escape detection. This emphasizes the necessity for 
making the first inspection early, preferably before leafhoppers or 
other sucking insects have appeared on the plants. 

This procedure may result in perfect control or eradication of the 
disease or in partial control, the element of uncertainty bemg due to 
om' inabifity to control the carriers. By it their activity can be 
rendered less effective by reducing the sources of inoculum to a 
minimiun. It has effectually halted the progress of the disease into 
new territory in Porto Rico. 

ELIMINATION BY GRINDING ALL CANE AND SECURING CLEAN SEED. 

In badly infested sections the problem is manifestly complicated. 
Where 25 to 60 per cent or more of the plants in large fields are 
diseased, roguing is obviously out of the question. Such plantings 
should be allowed to matm-e. Every stalk of it should be ground, 
however, and the stubble plowed up and kiUed. This means, of 
course, that carefully selected seed must be imported for replanting. 
Fortunately there is still an abundance of healthy stock in Louisiana 
and other cane sections in the United States. As a result of its 
recent exhaustive survey for mosiac disease, the Ofiice of Sugar- 
Plant Investigations of the Bm'eau of Plant Industry is in a position 
to furnish information on the nearest or m.ost accessible som'ce of 
clean seed for any region. Data have been secured on the prevalence 
of other diseases and msect pests in all cane regions, so that reason- 
able security against the dissemination of other cane maladies is 
assured. 

EXCLUSION. 

There are at the present time (October, 1919) a number of large 
cane areas in the United States not yet mvaded by the mosaic 
disease. Cane planters in these areas should urge the enactment of 



MOSAIC OF SUGAR CANE AND OTHER GRASSES. 



23 



State legislation prohibiting the importing of cane into them from 
any source whatever until such time as it can be accompanied by an 
authentic certification of health. Such areas include the entire 
Bayou Teche district and the parishes to the north in Louisiana, 
consisting of St. Mary, Iberia, Vermilion, Lafayette, St. Martin, 
Acadia, St. Landry, Avoyelles, and Rapides. This is, of course, 
the most important disease-free area. (Fig. 2.) Other similar 




Fig. 3.— Map of Louisiana, sho\ving the location of diseased areas of sugar cauo in that State. 

areas are the entire State of Mississippi with the exception of Biloxi; 
the entire State of Alabama except a small locality near Muscogee, 
Fla. ; the entire State of Georgia except Grady County; and all parts 
of Florida other than those indicated in figure 4. 

ERADICATION.! 

Wliere the disease is present in small amomit and in few well- 
defined areas, the possibility of quick and complete eradication 
exists. Such conditions are found in Mssissippi, Alabama, and 
Florida. (See fig. 1.) The cane in these areas should all be ground' 
during the present hai^vesting season -and the stubble plowed up. 
As a precautionary measure, some crop other than a grass should 
be grown on the land for one year, after which cane may again be 
grown with safety. The two small infested areas iii Alabama and 

1 In so far as it applies to the regions Indicated, we concur in this suggestion by Mr. Wilmon Newell, 
Plant Commissioner of Florida. 



24 



BULLETIlSr 829, U. S, DEPARTMENT OF AGPJCULTUEE. 



Mssissippi offer no diiE-culty at all. They can be destroyed with 
practically no loss to the owners, and the assurance of healthy crops 
in the future more than offsets the inconvenience of growing some 
other crop on the land now occupied by infected cane. The success 
of the measure in Florida is made possible by the present organization 
of the State plant board, which has already met the test of success- 
fully handling more serious problems. 

ELIMINATION BY PLANTING IMMUNE VARIETIES. 

Success of the control measures suggested up to the present depends 
entirely upon the whole-hearted cooperation of all cane growers. 




Fig. 4. — Map of Florida, sho^^•ing the location of diseased areas of sugar cane in that State. 

There yet remains a method, applicable only to certain regions, by 
which a planter can make himself wholly independent of any default 
on the part of his neighbors. A few varieties of sugar cane have been 
discovered that are absolutely immune to mosaic under all condi- 
tions. Most of them are of the type referred to as Japanese cane. 
Their origin is obscure. They have certain characteristics in com- 
mon. All are tall growing with slender stalks. They stool abund- 
antly, ratoon well, and produce an enormous tonnage. The sucrose 
content is not so high as in some of the broad-leaved canes, but in 
sugar per acre they take first rank with the best existing varieties. 
The Kavangire, Zwinga, Uba, Cayana 10, and numerous others 
imported by the office of Foreign Seed and Plant Introduction are 



MOSAIC OF SUGAR CAI^E AND OTHER GRASSES. 



25 



included among these varieties. The Cayana 10 has already won a 
well-deserved popularity among the farmers of the cane-sirup 
section in Georgia and northern Florida on account of its high 
tonnage and the excellent quality of sirup made from it. The Kavan- 
gire is used for manufacturing sugar in Argentina. Its estimable 
qualities are brought out in Table III. 




Fig. 5.— Kavangire sugar cane (immune), at the left; G. C. 1070 (susceptible), at the center; Java 36 (sus- 
ceptible but tolerant), at the right. 

Table III. — Yield and analysis of Kavangire sugar cane compared with other standard 

varieties.^ 



Variety. 


Average 
weight 

of single 
canes. 


Weight 
of cane 

per 
hectare.3 


Brix 
scale. 


Sucrose. 


Purity. 


Weight 
of sugar 

per 
hectare.3 




Kilos. 2 
0.68 
1.36 

.84 
1.87 
1.10 
1.71 

.95 
1.28 
1.23 
1.00 

.95 


Kilns. 2 

166,850 

117,300 

95,725 

118,125 

89,975 

94,150 

75,550 

72,925 

76,575 

79,675 

33,325 


Degrees. 
17.84 
17.55 
17.54 
17.32 
16.67 
18.26 
19.02 
16.69 
16.98 
16.03 
19.15 


Per cent. 
15.68 
15.34 
15.79 
15.34 
14.41 
16.39 
16.66 
14.54 
14.36 
13.57 
17.50 


Per cent. 
87.5 
87.4 
89.96 
87.05 
86.40 
89.74 
87.08 
87.07 
83.88 
89.68 
91.54 


KilO.t. 2 

16 090 


Java 36 


11 024 


Java 213 


9,533 
10 973 


Louisiana 60 


Java 139 


7 853 


Ravada (Louisiana Striped) 


9,714 
7 703 


Java 234 


Morada (Louisiana Purple (?)) 


6 '3.54 


Honduras 

Java 100 


5,998 
6,456 
3,940 


Tamarin 





1 Bennett, A. G. Informe de subestaciones para el aflo 1914. In Rev. Indus, y Agr. Tucuman, ano 5, 
p. 208-209. 1914. 

2 A kilo is the equivalent of 2.2 pounds. 3 ^ hectare is the equivalent of 2.47 acres. 



26 BULLETIN 829, U. S. DEPARTMENT OF AGRICULTURE. 

Figure 5 shows a row of Kavangire cane on the left; a susceptible 
variety, G. C, 1070, at the center; and a diseased but tolerant variety, 
Java 56, on the right. Unfortunately, the Kavangire variety is a 
long-season cane and therefore not suitable for conditions in Louisiana. 
The possibility of breeding more early maturing varieties from these 
parents is being investigated. 

Several of the broad-leaved varieties of cane originated at the 
Sugar Cane Experiment Station at Audubon Park, La., appear to be 
immune. Although equally exposed to the contagion, no individuals 
of these varieties have becom.e affected, while practically every plant 
of the scores of other varieties surrounding them is diseased. They 
have been under observation for too short a time, however, to 
demonstrate that their apparent immunity is permanent. 

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